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I’m not sure if this Solar Roadways concept is insane or brilliant, but I think my gut reaction is that this is generally far fetched – at least on the scale these visionaries are thinking about. Having noted that, I also think it might be useful for some specific roadway signage applications in the short run. Regardless of my thoughts, however, the SR idea apparently made enough sense to the U.S. Department of Transportation to get the agency to tentatively agree to give a $100,000 SBIR Phase I grant to the Idaho-based SR group to build a prototype.

Here is SR’s idea: Create full roads out of structurally-engineered solar panels. Yes, they would be driven on! These panels would provide a road surface, and collect and store energy to a LED transportation communications system built into some of the panels. Excess power would be pushed into the grid for residential and commercial use.

SR proposes making three-layered panels:

• The surface layer: Traction-designed, weatherproof and translucent. High-strength glass?
• The electronics layer: Primarily the PV layer, but with LEDs for “painting” and signage built into the road surface, and ultracapacitors for energy storage.
• The base plate layer: This layer insulates the upper layers, and distributes power and data signals.

SR says that it expects that each panel could produce 7600 Wh and 3.344MWhr per lane, per mile of electricity based on 15% efficiency and four hours of sunlight per day (for more details, see their Numbers page).

The issue of glass strength isn’t really addressed head on by SR. An FAQ on SR’s website has some discussion about traction issues, and mentions that presentations have been made at an International Workshop on Scientific Challenges for New Functionalities in Glass workshop and to Penn State’s Materials Research Institute, but fails to making a convincing case about whether current glass materials are up to the task that the SR concept poses.

One of SR’s weaker arguments is that the group envisions these panels as needing little maintenance (”Hey - we can use self-cleaning glass technology!”) and eliminating snow plowing (”Hey - they can heat themselves. No more snow/ice removal and no more school/business closings due to inclement weather!). For a company based in Idaho, they seem oblivious to the notion that state DOTs spend a lot of time and money on snow and ice removal despite (and because of) the fact that current roadways act already as heat sinks. SR panels would also be vulnerable to snow drifting.

Here is Scott Brusaw, one of SR’s key figures, discussion the proposition:

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Credit: David Shankbone

The New York Times reported last week that the price of solar panels has dropped 40 percent in a little more than a year.

That’s good news for consumers who have been scared off by the initial upfront costs for installing a solar array. The federal 30 percent subsidy for renewable energy projects has helped increase the number of installations and the number of the number of consumers willing to consider these units. State and local incentives have been helping, too. When coupled with falling panel prices, the all-important payback period can be significantly reduced.

But the news is probably a mixed bag for panel makers. Clearly, more efficient manufacturing has been a factor, but so, too, has heighten competition. According to the article, materials sourcing and manufacturing in China may be a bigger factor:

Until recently, panel makers had been constrained by limited production of polysilicon, which goes into most types of panels. But more factories making the material have opened, as have more plants churning out the panels themselves — especially in China.

“A ton of production, mostly Chinese, has come online,” said Chris Whitman, the president of U.S. Solar Finance, which helps arrange bank financing for solar projects.

While business is up for solar installers, the Times reports that some domestic PV makers are still losing money. Some market watchers have been cautioning about the possibility that elements of the solar manufacturing industry were facing a major downturn in revenues and venture capital because of a purported beginnings of an oversupply of PV units. In early 2008, we reported in the ACerS Bulletin (see p. 5) that Lux Reseach Inc., for example, said supply will begin to “exceed demand in 2009, leading to falling prices and a shake-out among companies, particularly crystalline silicon players that haven’t invested in thin-film technologies.”

A recent posting on Lux’s blog notes that many well-known PV manufacturers didn’t show at the July Intersolar conference, but a host of Chinese companies had a big presence.

In a somewhat related followup story, the Times also reports on how a shift to the use of microinverters on each panel can decrease performance problems sometimes experienced with multipanel arrangements and allow consumers to install an initially small solar system but add more panels later as the prices drop.

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Depiction of chromophores attaching to a transistor made from a single carbon nanotube. Credit SNL.

Research being conducted at Sandia National Lab might eventually be applied to an optical detector with nanometer-scale resolution, ultra-tiny digital cameras, solar cells with more light absorption capability and a better device for genome sequencing. However, the near-term purpose of the research is basic science.

The Sandia researchers report they have created the first carbon nanotube device that can detect the entire visible spectrum of light. This might allow them to study single-molecule transformations, how the molecules respond to light and change shape as well as other fundamental interactions between molecules and nanotubes.

As with many other recent studies, the researchers went back to nature, in this case the human eye, and they improved on the model. A cascade of chemical and electrical events that ultimately trigger nerve impulses occur when light strikes a chromophore on the molecules in the eye’s retina. Likewise, when light strikes a chromophore in the nanoscale color detector, it causes a conformational change in the molecule. This, in turn, causes a threshold shift on a transistor made from a single-walled carbon nanotube.

“In our eyes the neuron is in front of the retinal molecule, so the light has to transmit through the neuron to hit the molecule,” says Sandia researcher Xinjian Zhou. “We placed the nanotube transistor behind the molecule - a more efficient design.”

That carbon nanotubes are light sensitive has been known for a long time, but earlier efforts using an individual nanotube were only able to detect light in narrow wavelength ranges, and then only at laser intensities. The Sandia team nanodetector is orders of magnitude more sensitive, down to about 40 W/m2, which is about 3 percent of the density of sunshine reaching the ground. “Because the dye is so close to the nanotube, a little change turns into a big signal on the device,” says Zhou.

Zhou and his colleagues François Léonard, Andy Vance, Karen Krafcik, Tom Zifer and Bryan Wong created the device, which they described in a paper published in Nano Letters. Zhou and Krafcik created a tiny transistor made from a single carbon nanotube. They deposited carbon nanotubes on a silicon wafer and used photolithography to define electrical patterns to make contacts. Meanwhile, Vance and Zifer synthesized molecules to create three types of chromophores that respond to either red, green or orange bands of the visible spectrum. Zhou immersed the wafer in the dye solution until the chromosphores attached themselves to the nanotubes.

“Detection is now limited to about 3 percent of sunlight, which isn’t bad compared with a commercially available digital camera,” says Zhou. “I hope to add some antennas to increase light absorption.”

The team is now working on detecting infrared light. “We think this principle can be applied to infrared light, and there is a lot of interest in infrared detection,” says Vance. “So we’re in the process of looking for dyes that work in infrared.”

“A large part of why we are doing this is not to invent a photo detector, but to understand the processes involved in controlling carbon nanotube devices,” says Léonard, author of The Physics of Carbon Nanotubes, published September 2008.

The next step is to create a nanometer-scale photovoltaic device. Such a device on a larger scale could be used as an unpowered photo detector or for solar energy. “Instead of monitoring current changes, we’d actually generate current,” says Vance. “We have an idea of how to do it, but it will be a more challenging fabrication process.”

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Schott's Chairman Udo Ungeheuer (right), Gov. Bill Richardson (second from right) and other state and company officials autograph the first CSP unit.

Schott Solar this week cut the ribbon on new $100 million facility in Albuquerque to produce large-scale concentrated solar power receivers and PV units. Schott, which also has production facilities in Germany, the Czech Republic and Spain, says the 200,000 square-foot plant will provide at least 350 jobs, and is being described as only the first phase of the company’s plan. Schott has another PV facility in Billerica, Mass.

The plant was designed to facilitate anticipated future growth. In subsequent phases, Schott says the buildings can expand to 800,000 square feet and ultimately employ 1,500 workers.

The new production plant has annual capacity of 85 MW of 225-watt polycrystalline PV modules. These units will be sold under Schott Solar Poly 225 brand and marketing is targeted at commercial buildings and schools. Schott will also run two production lines for manufacturing parabolic trough, utility-scale CSP units. Combined, these two lines have an annual CSP capacity of 400 MW.

Schott CSP technology is based on heat-exchange system. A heat transfer fluid resides in steel absorber tubes encased in evacuated glass tubes. The tubes are positioned at the focal point of the mirrors. The fluid moves through a heat exchanger/boiler apparatus, creating steam used to drive a turbine generator.

Schott and at least one state official linked the plant opening to increased investments in renewable energy sources contained within the federal American Recovery and Reinvestment act. “This facility is proof that smart policy can create jobs and spur investment,” said New Mexico Governor Bill Richardson. “SCHOTT Solar has recognized the vast potential that exists for solar energy in the United States and especially New Mexico.”

Adding . . . where is a news broadcast about the opening:

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A new name in PV manufacturing, Skyline Solar, went public today with its business plans and demonstrations of its High Gain Solar arrays technology that it claims will bring the cost of solar power to competitive levels in the normal electricity market. The HGS system, which uses a novel parabolic reflector arrangement, is being targeted at commercial, government and utility markets.

Skyline’s announcement today is driven in part by the completion of a demonstration project build in partnership with the Santa Clara Valley Transportation Authority in San Jose, Calif. (see time-lapse video at the facility, above). The company says the project was completed in eight months and now provides power for a maintenance facility and serves as a proof of concept for Skyline’s technology strategy.

Besides the reflector arrangement HGS features single-axis vertical tracking, plus compact PV collectors and convection cooling. In a news release, Skyline says, “HGS architecture delivers ten times more energy per gram of silicon versus traditional flat-panel systems in sunny locations and offers industry-leading energy density.”

Like other concentrator systems, Skyline says it can use less silicon (90 percent less) and produce more power. The company also says savings comes from having a system that has 66 percent fewer parts versus traditional single axis tracking systems. Besides cutting manufacturing costs, fewer parts presumably means lower maintenance costs.

Skyline says that pilot manufacturing of HGS components is underway in the U.S. and Asia. It has received $24.6 million venture financing from New Enterprise Associates and has signed a developmental contract with the DOE for $3 million. Skyline Solar was selected as one of six solar photovoltaic technology companies to receive a grant under the DOE’s Solar America Initiative. The company was cited as developing a technology that could “make solar energy cost-competitive with conventional forms of electricity.”

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